Project Summary We will address two major weaknesses in previous studies examining the association of air pollution with perinatal outcomes. The first weakness, exposure error, will be addressed by linking a comprehensive and large birth database with spatially and temporally resolved exposure estimates from an advanced exposure modeling system. The second weakness, namely, minimal knowledge concerning time-activity and behavior changes that affect women's personal exposures during pregnancy, will be addressed by following a prospective cohort using questionnaires and GPS time-activity sampling. Outcomes include low birth weight (LBW) and preterm delivery (PTD). Exploratory analysis will be conducted for ultrasound outcomes in the prospective cohort. The long-term goal will be to develop methods that can be applied to a large population- based study of births that will include more intensive outcome and exposure assessments, as well as assessments of maternal-fetal genetic variation. The specific aims are as follows: 1) To determine the association of mothers'residential exposure to traffic-related air pollutants with LBW and PTD in a large retrospective cohort. We will study this birth cohort (N=97,500) with detailed clinical data for the mother during pregnancy. Outdoor concentrations of polycyclic aromatic hydrocarbons (PAH), nitric oxide (NO), and nitrogen dioxide (NO2) at each residence will be estimated and summarized by month and trimester for each subject. Logistic regression will be performed adjusting for known or suspected confounding factors not generally available in birth registries. In utero windows of vulnerability to air pollutants will be examined. 2) To test prospective recruiting methods and develop data collection instruments that can be used in a planned larger study using ultrasound data. We will prospectively recruit 100 subjects during their first prenatal visit. The subjects will be followed by an environmental and behavior questionnaire coupled with one-week GPS sampling three times during their pregnancy. Changes in time-activity and air pollution exposures during pregnancy will be assessed. In addition, methods will be developed to examine the association of air pollution with ultrasound outcomes (e.g. head circumference), which may serve as biomarkers of in utero growth restrictions. 3) To test measurement and modeling methods. We will conduct extensive exposure measurements for 40 of the prospective subjects, and models will be developed and validated to estimate outdoor, in-transit and personal exposures. Model performance will form the basis for the design of a larger study. Project Narrative The knowledge that will emerge from this study will be of benefit to public health by identifying and describing environmental factors affecting adverse birth outcomes. This research is expected to have an impact on decisions regarding the protection of health in pregnant women who are susceptible to the adverse effects of air pollution.